1. Field of the Invention
The invention pertains to a hydrodynamic torque converter of the type having a converter housing containing a pump wheel, a turbine wheel and a stator forming a hydrodynamic circuit; at least one axial bearing supporting the stator; and a support element for each axial bearing, the support element having a bearing side in contact with the axial bearing, and a stator side, facing away from the axial bearing, in contact with the stator. At least one flow passage connects at least one flow conduit to said hydrodynamic circuit, the flow passage being defined by a flow bed facing the stator and at least one boundary wall extending from the flow bed to the stator side of the support element.
2. Description of the Related Art
A torque converter of this type is known from, for example, DE 197 52 187 A1. The torque converter has a converter housing to hold at least one pump wheel, one turbine wheel, and one stator, where the wheels just mentioned serve to create a hydrodynamic circuit. The stator is positioned by an axial bearing arrangement on each side, where a support element assigned to the axial bearing arrangement is provided axially between a component of the stator, especially its freewheel, and said axial bearing arrangement. Each of these support elements has a bearing side, which faces the axial bearing arrangement, and a stator side, which faces the freewheel of the stator. These support elements have flow passages for viscous medium, so that in this way a connection can be established between at least one flow conduit connected to a pressure source and the hydrodynamic circuit. The flow passage has a flow bed and boundary walls adjacent thereto on both sides, which lead from the flow bed to the axial level of the bearing side of the support element.
In these types of torque converters, needle bearings are usually used as the axial bearing arrangements, which for cost reasons are designed as so-called xe2x80x9ccompact bearingsxe2x80x9d. These are characterized in that they have two relatively thin bearing disks, which can rotate relative to each other, between which the rolling elements are installed.
Because relatively high axial forces are exerted on these axial bearing arrangements, it is possible, especially when the support elements are designed with large-volume flow passages on the bearing side, for the bearing disk adjacent to this flow passage to be plastically deformed by the pressure exerted on it by the rolling elements of the compact bearing and thus pressed into the flow passage, which ultimately leads to damage to the axial bearing arrangement and to a narrowing of the flow passage. To reduce the severity of this problem, it is possible, of course, as done in DE 197 52 187 A1, to design the flow passage with a large component extending in the circumferential direction so that radial contact surfaces for the bearing disk of the compact bearing can be provided at all times on the bearing side of the support element in spite of the flow passages, but this results in an undesirable increase in the distances which the viscous medium must travel within the flow passages. Despite these design measures, plastic deformations of the bearing disk in question can still not be completely excluded.
The invention is based on the task of improving the support elements assigned to axial bearing arrangements in such a way that these elements prevent damage to the bearing disks especially of a compact bearing and nevertheless allow the viscous medium to flow at a comparatively high rate over a short distance.
According to the invention, the bearing side of each support element is essentially flat, and the stator side is provided with at least one flow passage provided with a stiffener connecting the flow bed and the at least one boundary wall. As a result of the essentially flat design of the bearing side of the support element, i.e., the side of the support element facing the axial bearing arrangement, the conditions are created under which a bearing disk on the axial bearing arrangement, especially an axial bearing arrangement designed as a compact bearing, receives support with no interruptions on the bearing side of the support element, with the result that especially the axial forces exerted by the rolling elements of the axial bearing arrangement can be transmitted over a large area via the bearing disk to the adjacent support element.
To prevent the bearing side of the support element from undergoing plastic deformation upon the introduction of axial forces, the minimum of one flow passage, which, according to the invention, is provided on the stator side of the support element, i.e., on the side of the support element which faces away from the axial bearing arrangement, with a stiffener in the area over which it extends. By establishing at least a partial connection between the flow bed of the flow passage and the minimum of one boundary wall, this stiffener makes the flow passage more resistant to deformation, but it also has the ability to absorb the axial forces being exerted on the flow bed of the flow passage, which have been absorbed on the bearing side of the support element, and to transmit them onward via the minimum of one boundary wall to the stator side of the support element, so that these axial forces can then be introduced directly into the component (such as the outer freewheel ring) of the stator adjacent to the stator side of the support element. The stiffener is preferably provided on the flow bed at a point where the bed is more susceptible to deformation and where as a result the strength provided by the stiffener is especially effective.
Because the stiffener is located within the flow passage and projects from the flow bed toward the stator side of the support element, the stiffener does not take up any room. In addition, the stiffener can function as a flow guide within the flow passage. A stiffener, especially the stiffener on the engine-side support element, can be given the function of a throttle element, which constricts the flow passage. This is explained below:
Normally, the flow passage in the support element on the transmission side is used to supply the hydrodynamic circuit with fresh viscous medium, whereas the flow passage in the engine-side support element is used to allow the return of the viscous medium. It is therefore easy to regulate the flow rate in the hydrodynamic circuit via the engine-side flow passage. For this purpose, the engine-side flow passage can have a smaller volume flow rate than the transmission-side flow passage. This volume flow rate can be made even smaller by the stiffener, which projects into the flow passage and thus constricts the flow passage.
Simultaneously, the stiffener can also be used to reduce, if not to eliminate, any residual leakage which may occur from the transmission-side flow passage into the engine-side flow passage; this residual leakage tends to occur primarily in the area where the rolling elements of the freewheel have their radial dimension. The stiffener can reduce the severity of the residual leakage problem by diverting the medium arriving from the transmission-side flow passage back toward the side of its origin, or the stiffener can close off the engine-side flow passage completely or at least almost completely to the viscous medium arriving via the residual leakage connection.
According to advantageous elaborations, the flow passages extend essentially in the radial direction, so that the viscous medium travels only a short distance within the flow passages. Because of the flat surface of the bearing side of the support element and because of the presence of the stiffeners in the flow passages, the flow passages can designed with very wide dimensions in the circumferential direction.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.